Method of magnetizing a driving tool



Nov. 10, 1970 G. B. STILLWAGON, JR 3,538,792

METHOD OF MAGNETIZING A DRIVING TOOL Filed Feb. 5, 1968 w! a 3 3 5 M. 2 6 I 0 2 8 m F FIG-.3

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United States Patent Oifice 3,538,792 Patented Nov. 10, 1970 3,538,792 METHOD OF MAGNETIZING A DRIVING TOOL George B. Stillwagon, .lr., Dayton, Ohio, assignor to Gardner-Denver Company, Dayton, Ohio, a corporation of Delaware Filed Feb. 5, 1968, Ser. No. 703,021 Int. Cl. B21k 21/00 U.S. Cl. 76-101 6 Claims ABSTRACT OF THE DISCLOSURE A fastener driving magnetic tool has an annular inner pole piece and an annular outer pole piece concentrically spaced with an annular thickness'orientated elastomeric strip magnet disposed therebetween. The inner pole piece is in radially expanded compressing relation against the magnet for retaining both the magnet and the inner pole piece, and an axially adjustable inner pole piece extension member or a non-magnetic tube member is disposed within the inner pole piece.

BACKGROUND OF THE INVENTION In the assembly of a fastener driving tool as disclosed in applicants copending application Ser. No. 507,916, filed Nov. 12, 1965, now Pat. No. 3,392,767, issued July 16, 1969, an elastomeric strip magnet is rolled into a tube or'cylinder and inserted into the annular or tubular outer pole piece. A cylindrical inner pole piece is machined so that at least a portion of its outer diameter is slightly greater than the free inner diameter of the inserted strip magnet and then the inner pole piece is pressed axially into the strip magnet.

Since the flexible strip magnet is rather soft and fragile, it has been found desirable to machine the outer diameter of the inner pole piece within very close tolerances and to form a pilot portion of slightly reduced outside diameter and a smooth outer surface so that when the inner pole piece is pressed axially into the magnet,

it will not strip or shear material from the magnet. It

has been found, however, that the close machining of the inner pole piece significantly increases the cost of the tool and the reduced pilot portion prevents full area contact of the inner pole piece with the magnet.

Due to the various types of commonly used nut fasteners, usually a socket type driving tool, as shown in the above application, is constructed for a particular type and size of nut. That is, the inner pole piece is positioned in precise axial spaced relation to the outer pole piece according to the thickness of the type of nut which is being used. It has been found desirable to construct such a socket so that it can accommodate nuts of different thickness.

There is also a specific problem presented by a socket as shown in the above application when threading a nut onto a tubular threaded stud from which projects a concentric magnetically attractable stem or shaft, for example, when assembling a rheostat to a control panel. That is, the stem is attracted to the inner pole piece thereby moving the shaft out of alignment with the socket and resulting in producing a bad start of the nut on the stud.

SUMMARY OF THE INVENTION for retaining the magnet not only eliminates the need for machining the inner pole piece within close tolerances and for forming a pilot portion of the inner pole piece but also eliminates the need for forming a smooth inner surface on the magnet. Furthermore, the expanded inner pole piece assures full area contact between the magnet and the inner and outer pole pieces thus providing maximum magnet utilization.

The present invention also provides a magnet fastener driving tool incorporating an inner pole piece extension member which is in axially adjustable relation to the inner pole piece so that one tool can accommodate threaded fasteners of various shapes and thicknesses. In another embodiment, the inner pole piece of a drive socket is lined with a non-magnetic tubular leeve member so that when the socket receives a shaft projecting concentrically from a tubular threaded mounting stud, alignment of the socket and stud is maintained and the nut is properly threaded on the stud.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is an axial section through a drive socket constructed in accordance with the invention;

FIG. 2 is an end view of the socket shown in FIG. 1 with a portion broken away;

FIG. 3 is an axial section similar to FIG. 1 and illustrating in exaggeration a method of assembling the socket in accordance with the invention;

FIG. 4 is an explored perspective view of the drive socket shown in FIG. 1;

FIGS. 5 and 6 show a modification of an inner pole piece extension member;

FIG. 7 is an axial section of a drive socket constructed in accordance with another embodiment of the invention;

FIG. 8 is a section taken generally on the line 8-8 of FIG. 7; and

FIG. 9 is an axial section of a further embodiment of a drive socket constructed in accordance with the vention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the figures of the drawing, FIG. 1 illustrates a magnetic pickup socket 15 constructed in accordance with the invention and of the type commonly referred to as a clearance socket particularly suited for driving a nut N onto a threaded bolt ,(not shown). The socket 15 includes a tubular body 16 forming an outer pole magnetic piece, and having a forward driving end portion 18 with a socket opening 20 of hexagonal cross-section for receiving the nut N. The body 16 also includes a rearward end portion 22 having a square opening 23 for receiving the square drive shank of a tool, such as a pneumatic wrench or a hand actuated socket wrench. The central portion of the body 16 has a cylindrical bore 24 in which is positioned a thickness orientated elastomeric magnet 25 formed or rolled into the shape of a cylinder from a strip magnet material as disclosed in the aforementioned application, and as shown in FIG. 4.

. A cylindrical inner pole piece 30 having an outer diameter slightly less than the inner diameter of the cylindrically shaped magnet 25, is inserted within the magnet 25 and expanded radially into compressing relation with the outer pole piece or body 16. One method of expanding the inner pole piece 30 is illustrated somewhat exaggerated in FIG. 3 wherein a metal ball or spherical mandrel 32 of a diameter greater than the inside diameter of the inner pole piece 30 is first positioned within the cylindrical bore 24 of the socket 15 as shown in the dotted portion adjacent the internal shoulder 33 formed by the opening 23. The magnet 25 and inner pole piece are then successively inserted into the bore 24, and the entire socket assembly is positioned on a tubular fixture having a portion 36 which is received within the socket opening 20. The fixture 35 provides an external shoulder 37 which abuts the end of the body 16, and an internal shoulder 38 forms a stop for the end of the inner pole piece 30.

A cylindrical bore 39 is formed within the fixture member 35 and has a diameter slightly larger than the spherical mandrel 3'2 but less than the outer diameter of the inner pole piece 30. While the socket 15 is firmly held on the fixture 35, a plunger 40 is inserted within the opening 23 and is pressed against the spherical mandrel 32 causing the mandrel to move towards the opening 39 within the fixture 35 thereby progressively expanding the inner pole piece 30' into radially compressing relation with the magnet 25.

While the use of the spherical mandrel 32 illustrates one method of expanding the inner pole piece 30, it is within the scope of the invention to expand the inner pole piece by other methods, as for example, by hydraulic pressure or by using an elongated plunger type mandrel. Furthermore, it is within the scope of the invention to employ a split inner cylindrical pole piece such as an elongated C-shaped spring sleeve and to contract or collapse the inner pole piece before inserting it into the magnet 25.

Referring to FIGS. 1, 2 and 4, an auxiliary inner pole piece or sleeve-like extension member having a longitudinally extending slot 46 and a C-shaped cross-sectional configuration, may be disposed within the cylindrical inner pole piece 30 and frictionally retained, so that it is frictionally adjustable in an axial direction with respect to the inner pole piece 30. The adjustability of the inner pole piece extension member 45 with respect to the socket opening 20 enables its end surface 48 (FIG. 1) to be precisely positioned in relation to the end of the body 16 according to the thickness of the nuts being driven in order to obtain a positive engagement between both the inner and outer pole pieces and the nut and thereby obtain the most effective magnetic attraction between the socket 15 and the nut.

Referring to FIGS. 5 and 6, a modified inner pole piece extension member 50 has a head portion 51 with a diametrically extending slot 52 which continues throughout the length of the extension member to provide a C- shaped cross-sectional configuration substantially the entire length of the extension member. The head portion 51 provides the extension member with an end surface which permits convenient adjustment of the extension member relative to the expanded inner pole piece 30.

FIGS. 7 and 8 show another embodiment of a socket member constructed in accordance with the invention. In this embodiment, the socket body 16 retains a cylindrical shaped magnet 25' and an expanded cylindrical inner pole piece 30' which, in turn, slidabl receives an extension member 55 having a forward end face 56 and a blind hole 57 in its rearward end portion. A spiralhelical compression spring 58 has its smaller end received within the hole 57 and its larger end seats on the internal shoulder 33.

The inner pole piece extension member 55 has an outwardly flared rearward end flange 60 which engages the rearward end of the inner pole piece 30 to limit the forward movement of the extension member 55 under the force exerted by the spring 58. The minimum distance between the forward end face 56 of the extension member 55 and the forward end surface of the body 16 is preset to provide for positive engagement between the extension member and a relatively thin nut such as shown in FIG. 1. When the socket is used with a thicker nut, however, the extension member 55 moves reanwardly compressing the spring 58 to produce full engagement between the socket opening 20 and the outer peripheral surface of the nut While also maintaining positive engage- 4 ment with the nut for obtaining the maximum magnetic attraction between the socket and the nut. It is to be understood that the extension member 55 could be tubular and the spring 58 be constructed to engage the end sur face of the tubular member.

In accordance with another embodiment of the invention, a magnetic clearance socket 65 (FIG. 9) has a tubular body 66, a fastener receiving opening 68 and a square shank receiving opening 69. A rolled elastomeric strip magnet 70 is positioned within a counterbore 71 formed within the body 66, and a cylindrical inner pole piece 72 is expanded radially in the manner described above for retaining the magnet 70 and inner pole piece within the body 66. The socket 65 is ideally suited for use in threading a nut N onto a threaded tubular stud 74 of a rheostat 75 having an elongated stem or shaft 76 concentric with the threaded stud 74. When the shaft 76 is constructed from a magnetic material, the stem is prevented from being attracted to the inner pole piece 72 during starting of the nut N by an inner sleeve or tube 80 of a nonmagnetic material such as aluminum which is pressed fitted into the inner pole piece 72 thereby blocking the magnetic attraction between the shaft 76 and the inner pole piece 72.

From the drawing and the above description, it can be seen that a fastener driving magnetic tool constructed in accordance with the invention has several desirable features and advantages. For example, by expanding the inner pole piece 30 into radially compressing relation with the magnet 25, both the magnet and the inner pole piece are eifectively and positively retained within the body 16 without the need for maintaining extremely close tolerances and smooth finishes on the outer surface of the inner pole piece 30 and the inner surface of the cylindrically shaped magnet 25. Also, by the use of the mandrel 2, the magnet strip 25 and the pole piece 30 are accurately positioned with respect to the socket opening concurrently with the sizing step.

Another important feature is provided by the axially adjustable inner pole piece extension member 45, 50 or 55 which enables the socket to be conveniently and precisely adjusted for accommodating threaded fasteners of various thicknesses. Furthermore, the non-magnetic tubular member 80 shown in the embodiment of FIG. 9 conveniently adapts a magnet socket for accurately starting and driving a threaded fastener over an elongated concentric shaft which would otherwise be attracted towards the inner pole piece 72 causing the socket to tilt out of alignment with the axis of the shaft.

While the method of expanding the inner pole piece Within the magnet and outer pole piece is illustrated in the drawing in conjunction with the assembly of a clearance type socket, it is to be understood that the expanding technique may also be used for assembling other forms of annular magnets for fastener driving tools. For example, the magnet assembly shown in FIG. 6 of the above application for use on a screw driven bit may be accomplished by expanding the inner cylindrical pole piece within the outer cylindrical pole piece.

While the method and articles herein described constitute preferred embodiments of the invention, it is to be understood that the invention is not limited to this precise method and these articles, and that changes may be made therein without departing from the scope of the invention which is defined in the appended claims.

What is claimed is:

I. A method for magnetizing a fastener driving tool having a hollow outer pole piece, comprising the steps of inserting an annular resilient magnet within said outer pole piece, inserting an annular inner pole piece within said magnet, and radially expanding said inner pole piece into said magnet for radially compressing said magnet against said outer pole piece.

2. The method as defined in claim 1 wherein said step of radially expanding said inner pole piece comprises fixturing said inner pole piece relative to said outer pole piece, and inserting a mandrel axially into said inner pole piece.

3. The method as defined in claim 2 wherein said latter step comprises inserting a spherical said mandrel into said inner pole piece for progressively expanding said inner pole piece.

4. The metrod of manufacturing a magnetic pickup socket wrench comprising the steps of forming the socket wrench with a generally cylindrical opening inwardly of its driving end, positioning a generally annularly arranged thickness-oriented elastorneric strip magnet within said opening, positioning within said elastorneric strip magnet a generally tubular pole piece member, inserting a fixture into said opening for precisely locating said magnet and said pole piece member axially relative to said driving end, radially expanding said pole piece member into compressive relation with said strip magnet, and removing said fixture.

5. The method of claim 4 comprising the intermediate step of inserting a mandrel of a diameter greater than the inside diameted of said pole piece member into said socket opening prior to the insertion of said pole piece member, and in which said expanding step includes forcing said mandrel through said pole piece member outwardly through the driving end of said socket wrench.

6. A method of magnetizing a fastener driving tool having a hollow outer pole piece open at both ends, comprising the steps of inserting a resilient annular magnet within said outer pole piece, inserting an annular inner pole piece within said magnet, inserting a fixture into one end of said outer pole piece for positioning said inner pole piece and said magnet axially relative to said end of said outer pole piece, pressing a mandrel through said inner pole piece from the opposite end of said outer pole piece for radially expanding said inner pole piece into said magnet and radially compressing said magnet against said outer pole piece, and removing said fixture from said outer pole piece.

References Cited UNITED STATES PATENTS 3,016,501 1/1962 Gardner et a1 29-507 XR 3,253,626 5/1966 Stillwagon et al 5O BERNARD STICKNEY, Primary Examiner US. Cl. X.R. 29507, 523 

